Rheological Evaluation of Emulsifying Agent-Added Asphalt Binder for Cement Asphalt Mortar (CAM) Design by Means of Optimized Master Curve Modeling Approach

Designing an optimized Cement Asphalt Mortar (CAM) is essential not only for providing smoother riding quality on road pavements but also for reducing vibration and noise on railways. In producing CAM material, a crucial factor is the selection of asphalt binders with good mixing compatibility when combined with various emulsifying agents. Many emulsifying agents and corresponding modified asphalt binders have been studied and developed over the past decades to improve the material performance of the asphalt mixture. However, mechanical properties of blends of asphalt binder and emulsifying agents have not been studied or considered significantly from a perspective of application to railways. This demands a dedicated evaluation of these asphalt binder blends using various mathematical models in an attempt to design a better-performing CAM. In this paper, a rheological evaluation of asphalt binder mixed with three emulsifying agents was performed with different mathematical models, including a newly developed formulation called the C2MKP model. Dynamic Shear Rheometer (DSR) tests were conducted as experimental work. Complex modulus and phase angle results were computed; then, a corresponding master curve was generated based on different mathematical models. All the results were compared visually on a wide range of given test frequencies. It was found that modified asphalt binder can provide rheological performance similar to that of conventional asphalt binder, suggesting that modified asphalt binder can be successfully adopted in CAM production for railways.